While uninstalling Exchange Server 2003 (after a successfull migration to Exchange Server 2010) I ran into the dreaded “The server cannot be removed because” issue:

The server <servername> cannot be removed because:

– One or more users currently use a mailbox store on this server. These users must be moved to another mailbox store on a different server or be mail disabled before uninstalling this server.

Facility: Exchange System Manager

ID no: c103f492

Since I moved all resources from Exchange 2003 to Exchange 2010 I was sure there were no mailboxes left on Exchange 2003. Heck, the Mailbox databases and the Public Folder databases were already removed one day earlier so it had to be something else.

Open Active Directory Users and Computers (on the Exchange 2003 Server) and start the Find option. In the Advanced tab select Exchange Home Server in the Field drop-down box, select Ends with in the condition drop-down box and in the value type the last part of the Exchange 2003 server name.

In my case some users were returned that used to have a mailbox a long time ago but these were not used anymore.

Right click the user, select Exchange Tasks and select Remove Exchange Attributes. Now all Exchange (2003) related properties will be removed. Wait for replication to finish (in a larger environment) and the server be removed from the Exchange System Manager.